Investigation of effect of various drug loading and addition of a rate modifying agent on famotidine release from in situ forming implants

In this study, effects of drug loading and a rate-modifying agent on in vitro famotidine release from injectable in situ forming implants were investigated. Implant formulations contain specific amount of solvent and polymer, but different drug loading (4%, 8% and 11%). For the preparation of the formulations, N-methyl-2-pyrrolidone (NMP) was used as solvent while poly(DL-lactide-co-glycolide) (Resomer RG 503) was used as polymer and after injection into an aqueous environment, NMP diffusion led to polymer precipitation and the formulation showed acceptable regular release of drug for 2 weeks. Results showed that the amount of drug released (47.63%) over the first 24 hours (burst phase) for 4% drug loading system, was significantly higher than that of 8% loading (40.11%) and 11% drug loading (32.18%).Addition of ethyl heptanoate as a rate-modifying agent also demonstrated a reduction in the burst release. This effect might be due to decreasing the exchange rate of solvent and nonsolvent